Melinda Gates
Her husband founded Microsoft, changed the way we think about computers and is a billionaire more than 50 times over, but Melinda Gates is anything but a sidekick. She earned degrees in computer science and economics at Duke and an MBA from Duke's Fuqua School of Business, helped develop Microsoft's Publisher, Encarta and Expedia Programs and, as co-chair of the Bill and Melinda Gates Foundation, the largest private foundation in the world, has taken on causes as varied as global health, agriculture development and education. When TIME named its person of the year in 2005, it actually named three: Melinda, Bill and U2 lead singer Bono, their partner in philanthropy. Even though Bill and Bono may usually get most of the press, Mrs. Gates ensures their biggest project is not a one man show.